1. Field of the Invention
This invention generally relates to a dampening disk assembly. More specifically, the present invention relates to a separated hub type dampening disk assembly.
2. Background Information
A clutch disk assembly or dampening disk assembly used for a clutch of a car has a clutch function of coupling and/or uncoupling a flywheel of the engine to the transmission shaft, and a dampening function of absorbing and dampening torsion vibrations transmitted from the flywheel. The clutch disk assembly basically includes a clutch disk, a pair of input plates, a hub and an elastic portion. The pair of input plates are fixedly coupled to the clutch disk. The hub is disposed on the inner circumferential side of the input plate. The elastic portion elastically couples the hub and the input plates together for movement in a rotary direction. The elastic portion is disposed between the input plates and the hub, and is compressed in a rotary direction when the input plate rotates relatively against the hub. When the clutch disk assembly is coupled with the flywheel, a torque is inputted to the input plates of the clutch disk assembly from the flywheel. The torque is transmitted to the hub via the elastic portion, and then is outputted to a shaft extending from a transmission. When a torque fluctuation is input to the clutch disk assembly from an engine, a relative rotation is caused between the pair of input plates and the hub, and the elastic portion is compressed repeatedly in a circular direction.
In addition, the clutch disk assembly has a friction mechanism. The friction mechanism is disposed between the input plate and the hub, and generates a friction resistance when both portions rotate relatively. The friction mechanism includes a plurality of washers and urging portions.
A separated hub type clutch disk assembly has a hub flange (separated flange) in which a conventional flange of a hub is separated from a boss, in addition the separated hub type clutch disk assembly has the boss and the hub flange both of which are coupled in a rotary direction by an elastic portion with a low rigidity. This clutch disk assembly has a large torsion angle between an input plate and the hub, in addition provides a rigidity of two steps (low rigidity-high rigidity).
The conventional separated hub type clutch disk assembly mentioned above includes, for example, a small friction mechanism formed between a retaining plate (one of a pair of input plates) and the boss of the hub, and a large friction mechanism formed between the retaining plate and the hub flange. The large friction mechanism includes a first friction portion which touches the hub flange and is connected with the retaining plate relatively unrotatably and axially movably, and a first urging portion which is disposed between the first friction portion and the retaining plate and urges the first friction portion against the hub flange side. The small friction mechanism includes a second friction portion which touches the flange of the hub and is connected with the retaining plate relatively unrotatably and axially movably, and a second urging portion which is disposed between the second friction portions and the retaining plate and urges the second friction portion against the flange side. In general, the first friction portion is set to have a friction coefficient larger than that of the second friction portion, and the first urging portion is set to have an urging force larger than that of the second urging portion. Therefore, the large friction mechanism generates a larger friction (high hysteresis torque) compared with the small friction mechanism.
Within a range of a torsion angle of the first step in which the hub flange and the hub rotate relatively, the elastic portion with a low rigidity is compressed, and the second friction portion of the small friction mechanism rubs the flange of the boss, resulting in a characteristic of low rigidity-low hysteresis torque. After the hub flange starts rotating together with the boss in a body, a relative rotation between the hub flange and a pair of input plates is caused. Within a range of this second step, an elastic portion with a high rigidity is compressed between the hub flange and a pair of input plates, and the second friction portion of the large friction mechanism rubs the hub flange, resulting in a characteristic of high rigidity-high hysteresis torque.
In the conventional separated flange type clutch disk assembly mentioned above, a coil spring as the elastic portion with a low rigidity is disposed within a concave part which is formed around external teeth of the hub and internal teeth of the separated flange. The friction mechanism of the first step includes the friction portion that rotates together with the retaining plate in a body and is disposed axially movably, and the urging portion, which is disposed between the friction portion and the retaining plate. The urging portion is compressed between the friction portion and the retaining plate in an axial direction, and urges the friction portion toward the flange side. In this clutch disk assembly, a predetermined cutout in which the spring is disposed has to be formed at the hub and the separated flange. In addition, a formation of the cutout result in a reduction of the number of the external teeth of the hub and the internal teeth of the separated flange. In other words, an area which both portions touch decreases and a bearing stress decreases. Consequently, a possibility of an abrasion and damage of both external and internal teeth increases.
In view of the above, there exists a need for a dampening disk assembly which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.